BURGAS, Bulgaria — He looked like any other impatient tourist checking the big board at airport arrivals: a lanky, long-haired man in a baseball cap with his hands in the pockets of his plaid Bermuda shorts, a bulky backpack hanging from his shoulders.

Minutes later, authorities say, the man, filmed by security cameras at the Burgas airport, would board a bus filled with young Israeli tourists and blow himself up, killing six others as well. Authorities looked Thursday for clues as to who he was, using his fingerprints, his DNA and his fake Michigan driver’s license.

Despite the uncertainty, Israel was quick to blame Iran and its Lebanese allies Hezbollah for the attack Wednesday, which killed five Israelis, including a pregnant woman.

Prime Minister Benjamin Netanyahu said the bombing “was carried out by Hezbollah, the long arm of Iran.” Iranian Foreign Ministry spokesman Ramin Mehmanparast called the accusation “baseless,” saying it was aimed at diverting world attention from Israel’s role in the assassination of Iranian nuclear scientists.

Israel has attributed a series of attacks on its citizens around the world in recent months to Iran and its Shiite proxies, threatening to escalate a shadow war between the two arch-enemies that has escalated over Israeli allegations that the Iranians are trying to build nuclear weapons.

The attack occurred shortly after the Israelis boarded a bus outside the airport in the Black Sea resort town of Burgas, a popular destination for Israeli tourists – particularly for high school graduates before they are drafted into military service. Burgas is about 400 kilometers (250 miles) east of the capital, Sofia.

On Thursday, Bulgarian television aired security camera footage showing the suspected bomber wandering in and out of the terminal shortly before the blast. He was dressed as a tourist himself, wearing a baseball cap, T-shirt, plaid shorts and sneakers with short white socks. He carried a large backpack with wheels.

Interior Minister Tsvetan Tsvetanov said the backpack contained the bomb, which detonated in the luggage compartment of the bus. The bomber was believed to have been about 36 years old and had been in the country between four and seven days, Tsvetanov said without elaborating.

“We cannot exclude the possibility that he had logistical support on Bulgarian territory,” the minister said.

Officials were using DNA samples to try to establish his identity. Bulgarian Prime Minister Boiko Borisov told reporters that a Michigan driver’s license was retrieved, but U.S. officials said there was “no such person in their database.” Michigan is home to one of the largest Arab communities in the U.S.

Bulgarian television aired footage of the license showing the name of Jacque Felipe Martin with an address in Baton Rouge, Louisiana. Michigan officials said they told the FBI that no one by that name had a valid Michigan license and that out-of-state residents cannot be issued one anyway.

The Israelis had just arrived on a charter flight from Tel Aviv carrying 154 people, including eight children. Some of them told Israeli television that they were just boarding the white bus in the airport parking lot for a ride to their hotel when the blast occurred.

Officials reported overnight that an eighth person had died, but later said that was incorrect.

On Thursday, Bulgarian authorities rushed 200 police to hotels where about 1,000 Israelis were staying just north of Burgas. A representative of the Ortanna tour company, which books tours from Israel, said about 10,000 Israelis had scheduled vacations in Bulgaria through the firm this summer and about half had canceled after the attack.

A military plane carrying 33 Israelis injured in the bombing arrived Thursday in Israel. At least two critically injured Israelis were sent to Sofia for treatment, according to the head of the Israeli military medical corps, Brig. Gen. Itzik Kreis.

A Bulgarian government plane was to fly home 100 other Israelis who were not wounded, but who want to cut short their vacation.

Since Iran’s 1979 Islamic Revolution, relations with Israel resembled a cold war with both sides warily watching each other and dealing blows through proxies, but with little direct conflict.

That began to change more than two years ago with the first targeted killing of an Iranian nuclear scientist, whose death Iran claimed was the work of Israeli hit squads. It was the first strike in what has become a suspected shadow war that has now touched three continents.

Last week, Cypriot authorities said they had arrested a 24-year-old man on suspicion of planning terror attacks. Cyprus radio said he was of Lebanese origin and carrying a Swedish passport. Netanyahu blamed Iran for the alleged plot.

Speaking Thursday from his Jerusalem office, Netanyahu said Iran and Hezbollah “attack and murder innocent citizens, families, young ones, children, people who went for an innocent vacation and whose sin is to be Israeli and Jewish.”

He said it was time for the world to accept that “Iran is behind the wave of terror” and was the most “dangerous country in the world.”

“A terror state cannot have a nuclear weapon,” he said. “The most dangerous country in the world cannot have the most dangerous weapons on Earth.”

Israeli Defense Minister Ehud Barak described Hezbollah as the “director executors” and vowed that Israel “will do all it can to find those responsible and punish them, both those who carried it out directly and those who dispatched them.”

In Berlin, German Foreign Minister Guido Westerwelle urged the Israelis to show restraint until “the real perpetrators and backers” are found.

Although Iran denies any role in the Bulgaria blast, Tehran claims Israel’s Mossad spy agency was behind the slayings of at least five Iranian nuclear scientists since 2010, as well as other clandestine operations, such as planting powerful computer viruses.

In April, computer malware known as Flame infiltrated key government networks in Iran and forced a temporary shutdown of Internet links at the Oil Ministry and a key oil shipment facility. In the most recent targeted killing of an Iranian scientist, a director of the country’s main uranium enrichment facility was killed in January when a magnetic bomb attached to his car exploded in Tehran.

Israel has not directly replied to the Iranian charges. But Israeli leaders have repeatedly said that “all options are on the table” in trying to disrupt Iran’s nuclear program – a phrase that is widely interpreted as meaning the possibility of a military strike and other measures that could include cyberwarfare.

Since the fall of communism, Israel has maintained friendly ties with Bulgaria, a European Union nation of 7.3 million that borders Greece and Turkey.

Bulgaria’s government resisted Nazi demands to deport Jews to death camps in World War II. Many of them migrated to Israel when the communists seized power after the war.

In Sofia, the capital, Mayor Yordanka Fandakova ordered a stronger police presence at all public places linked to the Jewish community. Some 5,000 Jews live in Bulgaria, most in Sofia.